The invention relates to a stapling device for stapling a stack of sheets by means of staples that are cut off from a staple wire supply and shaped in the stapling head region, the stapling device comprising a staple wire transport device which transports the staple wire a corresponding length as a function of the thickness of a sheet stack to be stapled, and further comprising a movable staple wire cutting element which positions the staple wire, as a function of the thickness of the sheet stack to be stapled, centrally with respect to a staple shaping element on the stapling head, in which:
the staple wire transport device can be driven by a stepping motor whose drive direction is reversible and which can be activated by a measuring device which determines the thickness of the stack to be stapled;
the stepping motor is coupled to the staple wire transport device by means of a coupling that is effective only in the staple wire transport direction;
the stepping motor is continuously coupled to a movable peripheral cam or radial cam unit which controls a displacement of the staple wire cutting element; and
the peripheral cam or radial cam unit has control segments which are associated with different sheet stack thicknesses, as defined by U.S. Ser. No. 09/044,191.
In the case of the stapling device as defined in U.S. Ser. No. 09/044,191, the staple wire is transported by a pair of transport rollers, of which one transport roller is driven. A radial cam unit, joined to the driven transport roller, is coupled to a staple wire cutting element in such a way that the radial cam unit can be moved back and forth. In order to allow the staple wire to be transported continuously forward, an overrunning clutch is interposed, which allows reversal of the rotation direction of the drive in order to move the radial cam unit back without changing the transport direction of the staple wire. With this device, however, it is not possible for the staple wire that has already been transported and is ready for staple shaping to be pulled back again, so that, for example, in the event of a malfunction, the staple wire can be transported back into its starting position.